Method and apparatus for performing sterilizing treatment on plastic container

Abstract

The present invention is a method and an apparatus for performing heating and sterilizing treatment on the inside of a PET bottle with a low heat resistance securely and without thermal deformation thereof, where a steam jetting nozzle is inserted into the bottle from a mouth portion thereof to jet steam from the nozzle, the steam is circulated inside the bottle to be exhausted from the mouth portion, the steam is caused to contact with a bottle inner face securely, and simultaneously cooling water is sprayed on an outer face of the bottle so that thermal deformation of the bottle wall face is prevented.

What is claimed is:  
     
       1. A method for performing a sterilizing treatment on a plastic bottle having a necked mouth portion comprising the steps of: 
       inserting a steam jetting nozzle into the bottle through the mouth portion of the bottle to be subjected to the sterilizing treatment with a clearance formed between the nozzle and an inner face of the mouth portion, the bottle being so positioned that the mouth portion of bottle which is placed in an inverted state is directed downward;  
       upwardly jetting steam into the bottle from the steam jetting nozzle and circulating the jetted steam in the bottle to exhaust the steam from the clearance between the steam jetting nozzle and the inner face of the mouth portion, and jetting steam toward the inner face of the mouth portion to heat the mouth portion; and  
       supplying cooling medium to an outer face of the bottle simultaneously with the step of jetting steam to cool a wall of the bottle.  
     
     
       2. A method for performing a sterilizing treatment on a plastic bottle according to  claim 1 , wherein the temperature of the steam jetted from the steam jetting nozzle is 95° C. or more. 
     
     
       3. A method for performing a sterilizing treatment on a plastic bottle according to  claim 1 , further comprising a step of jetting steam to an outer face of the mouth portion of the bottle after the step of jetting steam. 
     
     
       4. A method for performing a sterilizing treatment on a plastic bottle according to  claim 1 , wherein the cooling medium supplied to the outer face of the bottle is cooling water. 
     
     
       5. A method for performing a sterilizing treatment on a plastic bottle according to  claim 1 , wherein the cooling medium supplied to the outer face of the bottle is cooling wind. 
     
     
       6. A method for performing a sterilizing treatment on a plastic bottle according to  claim 1 , wherein the steam jetted from the steam jetting nozzle into the bottle is pure water steam where impurities are removed from steam supplied from a boiler. 
     
     
       7. A method for performing a sterilizing treatment on a plastic bottle according to  claim 1 , wherein the steam jetted into the bottle from the steam jetting nozzle is pure water steam generated by heating pure water in a heat-exchanger. 
     
     
       8. An apparatus for performing a heating and sterilizing treatment on an inner face of a plastic bottle having a necked mouth portion, comprising 
       a holding mechanism for holding a bottle to be subjected to sterilizing treatment, so as to invert the bottle in an inverted state where the bottle is inverted such that the mouth portion of the bottle is directed downwardly;  
       a steam jetting nozzle inserted into a mouth portion of the bottle, the nozzle having at least one first opening directed toward an inner face of a bottom of the bottle and at least one second opening directed to an inner peripheral face of the mouth portion, and the diameter of the steam jetting nozzle being smaller than the inner diameter of the mouth portion of the bottle, so that a clearance is formed between the inner peripheral face of the mouth portion and an outer peripheral face of the steam jetting nozzle; and  
       a steam supplying mechanism for supplying steam to the steam jetting nozzle, thereby jetting the steam from the first and second openings into the bottle, wherein the jetted stream from the first opening is circulated in the bottle and exhausted from the clearance between the steam jetting nozzle and the jetted stream from the second opening is directly in contact with the inner peripheral face of the mouth portion.  
     
     
       9. An apparatus for performing a heating and sterilizing treatment on an inner face of a plastic bottle according to  claim 8 , wherein the holding mechanism is provided with a grasping mechanism for grasping the mouth portion of the bottle, and the grasping mechanism is rotated 180° about a pivot axis, so that the bottle so held is placed in said inverted state. 
     
     
       10. An apparatus for performing a heating and sterilizing treatment on an inner face of a plastic bottle according to  claim 8 , comprising a mouth portion outer face nozzle for jetting steam towards an outer face of the mouth portion of the bottle. 
     
     
       11. An apparatus for performing a heating and sterilizing treatment on an inner face of a plastic bottle according to  claim 8 , wherein an opening/closing valve for shutting off steam supplied to the steam jetting nozzle is provided in the steam supplying mechanism, and a bypass valve for supplying a predetermined amount of steam to the steam jetting mechanism even when the opening/closing valve is in a closed state is provided so as to bypass the opening/closing valve in parallel therewith. 
     
     
       12. An apparatus for performing a heating and sterilizing treatment on an inner face of a plastic bottle according to  claim 8 , wherein an opening/closing valve for shutting off steam supplied to the steam jetting nozzle is provided in the steam supplying mechanism and a bypass passage for supplying steam to the steam jetting nozzle even when the opening/closing valve is in a closed state is formed inside the opening/closing valve. 
     
     
       13. A method for performing a sterilizing treatment on a plastic bottle comprising the steps of: 
       positioning the bottle so that the mouth portion of the bottle which is placed in an inverted state is directed downward;  
       upwardly raising a jetting nozzle so that the nozzle is inserted into the bottle through the mouth portion of the bottle, a clearance being formed between the nozzle and an inner face of the mouth portion,  
       supplying steam into the nozzle to upwardly jet the steam into the bottle from the steam jetting nozzle and circulating the jetted steam in the bottle to exhaust the steam from the clearance between the steam jetting nozzle and the inner face of the mouth portion, thereby performing sterilizing treatment of the bottle;  
       supplying cooling medium to an outer face of the bottle simultaneously with the step of jetting steam to cool a wall of the bottle;  
       stopping the supply of cooling medium;  
       controlling the steam jetted from the nozzle to prevent the nozzle from being cooled; and  
       downwardly moving the nozzle to be removed from the bottle, wherein said controlling step is maintained until the next sterilizing treatment starts.  
     
     
       14. The method according to  claim 13 , said step of supplying steam also jets the steam in a lateral direction to directly contact the inner face of the mouth portion. 
     
     
       15. An apparatus for performing a heating and sterilizing treatment on an inner face of a plastic bottle having a necked mouth portion comprising: 
       a table having a central axis;  
       a main body supporting the table to be rotated about its central axis, the table having an horizontal upper face;  
       a plurality of grasping mechanisms provided at peripheral portions of the table, the grasping mechanism grasping the mouth portion of the bottle conveyed and rotating 180° up and down so that the bottle is placed in an inverted state such that the mouth portion is directed downward;  
       a plurality of heating and sterilizing mechanisms mounted on the table to correspond the grasping mechanisms, respectively;  
       a plurality of cooling mechanisms mounted on the table to correspond the grasping mechanisms, respectively, each of cooling mechanisms cooling the bottle grasped by the grasping mechanism, upon rotation of the table;  
       each of said heating and sterilizing mechanism including a nozzle which is vertically moved between a stabilizing position where the nozzle is inserted in the bottled grasped by the grasping mechanism through the mouth portion with a circular clearance formed between the nozzle and the mouth portion, and a rest position where the nozzle is removed from the bottle, the nozzle having at least one opening; and  
       a steam supplying mechanism for supplying steam to all nozzles in the sterilizing states so that steam is jetted into the bottles from the nozzles, circulated in the bottles, and then exhausted from the clearance between the nozzles and the mouth portions.  
     
     
       16. The apparatus according to  claim 15  wherein a plurality of openings are provided in the nozzle to jet stream in upper and lateral directions. 
     
     
       17. The apparatus according to  claim 15  wherein said steam supplying mechanism supplies steam to all nozzles in the rest positions in a smaller amount than those in the sterilizing positions.